Semiconductor device having buried gate electrode structures

ABSTRACT

A semiconductor device includes first and second gate electrode structures and a connection plug. The first gate electrode structure is buried in a semiconductor portion and has array stripes inside a first cell array of transistor cells and a contact stripe outside the first cell array, the contact stripe structurally connected with the array stripes. The second gate electrode structure is buried in the semiconductor portion and has array stripes inside a second cell array of transistor cells. An array isolation region of the semiconductor portion separates the first and second gate electrode structures. The connection plug extends between a first surface of the semiconductor portion and the contact stripe of the first gate electrode structure.

PRIORITY CLAIM

This application is a Divisional of U.S. patent application Ser. No.13/934,630, filed Jul. 3, 2013, said application incorporated herein byreference in its entirety.

BACKGROUND

Power semiconductor devices like MOSFETs (metal oxide semiconductorfield effect transistors) are designed to sustain a high breakdownvoltage in a blocking mode and to provide a low on-state resistance in aconductive mode. Power semiconductor devices therefore usually include adrift region between a voltage-controlled body/channel region and adrain region. Increasing the length of the drift zone increases thevoltage blocking capability, but at the same time increases the on-stateresistance. A power semiconductor device may integrate two or moretransistors arranged in series, in parallel or in other configurationsin the same semiconductor die to implement specific functions and/or toobtain specific device characteristics. It is desirable to providereliable semiconductor devices and methods that provide a simple andcost effective manufacturing process.

SUMMARY

In accordance with an embodiment, a method of manufacturing asemiconductor device includes introducing at least a first and a secondtrench pattern from a first surface into a semiconductor substrate. Anarray isolation region including a portion of the semiconductorsubstrate separates the first and second trench patterns. At least thefirst trench pattern includes array trenches and a contact trench thatis structurally connected with the array trenches. A buried gateelectrode structure is provided in a lower section of the first andsecond trench patterns, in a distance to the first surface. A connectionplug is provided between the first surface and the gate electrodestructure in the contact trench.

According to another embodiment, a semiconductor device includes a firstand a second gate electrode structure buried in a semiconductor portion.The first gate electrode structure includes array stripes arrangedinside a first cell array of transistor cells and a contact stripeoutside the first cell array. The contact stripe is structurallyconnected with the array stripes. The second gate electrode structureincludes array stripes inside a second cell array of transistor cells.An array isolation region of the semiconductor portion separates thefirst and second gate electrode structures. A connection plug extendsbetween a first surface of the semiconductor portion and the contactstripe of the first gate electrode structure.

A further embodiment refers to a power semiconductor device with anactive drift zone. The power semiconductor device includes a first and asecond gate electrode structure which are buried in a semiconductorportion. The first gate electrode structure includes array stripesinside a first cell array of transistor cells and a contact stripeoutside the first cell array. The contact stripe is structurallyconnected with the array stripes. The second gate electrode structureincludes array stripes inside a second cell array of transistor cells.An array isolation region of the semiconductor portion separates thefirst and second gate electrode structures. A connection plug extendsbetween a first surface of the semiconductor portion and the contactstripe. A connection wiring directly adjoins active semiconductor areasof the transistor cells in the second cell array and the connectionplug.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification. The drawings illustrate the embodiments ofthe present disclosure and, together with the description, serve toexplain principles of the disclosure. Other embodiments and intendedadvantages will be readily appreciated as they become better understoodby reference to the following detailed description.

FIG. 1A is a schematic perspective view of a portion of a semiconductorsubstrate for illustrating a method of manufacturing a semiconductordevice in accordance with an embodiment relying on different trenchwidths for providing a self-aligned gate connection, after introducingtrench patterns into the semiconductor substrate.

FIG. 1B is a schematic cross-sectional view of the semiconductorsubstrate portion of FIG. 1A along line A-B-C after recessing a gatematerial deposited into the trench patterns.

FIG. 1C is a schematic cross-sectional view of the semiconductorsubstrate portion of FIG. 1A along line A-B-C after depositing adielectric fill material.

FIG. 1D is a schematic cross-sectional view of the semiconductorsubstrate portion of FIG. 1C after planarizing a deposited furtherconductive material forming a connection plug.

FIG. 1E is a schematic perspective view of the semiconductor substrateportion of FIG. 1D after providing separation structures and aconnection wiring.

FIG. 2A is a schematic circuit diagram of a semiconductor device inaccordance with an embodiment integrating an enhancement type IGFET(insulated gate field effect transistor) and a depletion type IGFET.

FIG. 2B is a schematic plan view of a portion of the semiconductordevice of FIG. 2A.

FIG. 2C is a schematic cross-sectional view of the semiconductor deviceof FIG. 2B along line A-B-C.

FIG. 3A is a schematic cross-sectional view of a portion of asemiconductor substrate for illustrating a method of manufacturing asemiconductor device in accordance with an embodiment relying on arecess mask for providing a self-aligned gate connection, afterproviding the recess mask.

FIG. 3B is a schematic cross-sectional view of the semiconductorsubstrate portion of FIG. 3A after recessing exposed portions of thegate material and providing fill structures.

FIG. 3C is a portion cross-sectional view of the semiconductor substrateportion of FIG. 3B in a plane parallel to the cross-sectional plane ofFIG. 3B.

FIG. 4 is a cross-sectional view of a portion of a semiconductor devicemanufactured according to the method of FIGS. 3A to 3C.

FIG. 5A is a circuit diagram of an ADZFET (active drift zone fieldeffect transistor).

FIG. 5B is a plan view of a wiring plane of the ADZFET of FIG. 5A inaccordance with a further embodiment of the invention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which are shownby way of illustrations specific embodiments in which the disclosure maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present disclosure includes such modifications andvariations. The examples are described using specific language thatshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only. Forclarity, the same or similar elements have been designated bycorresponding references in the different drawings if not statedotherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open and the terms indicate the presence of stated structures,elements or features but are not intended to preclude the presence ofadditional elements or features. The articles “a”, “an” and “the” areintended to include the plural as well as the singular, unless thecontext clearly indicates otherwise.

The term “electrically connected” describes a permanent low-ohmicconnection between electrically connected elements, for example a directcontact between the concerned elements or a low-ohmic connection via ametal and/or highly doped semiconductor. The term “electrically coupled”includes that one or more intervening element(s) adapted for signaltransmission may exist between the electrically coupled elements, forexample elements that temporarily provide a low-ohmic connection in afirst state and a high-ohmic electric decoupling in a second state.

The Figures illustrate relative doping concentrations by indicating “−”or “+” next to the doping type “n” or “p”. For example, “n−” means adoping concentration that is lower than the doping concentration of an“n”-doping region while an “n+”-doping region has a higher dopingconcentration than an “n”-doping region. Doping regions of the samerelative doping concentration do not necessarily have the same absolutedoping concentration. For example, two different “n”-doping regions mayhave the same or different absolute doping concentrations.

The method illustrated in FIGS. 1A to 1E relies on a semiconductorsubstrate 500 a consisting of or containing a semiconductor layer 100 aof a single-crystalline semiconductor material. The single-crystallinesemiconductor material may be silicon Si, silicon carbide SiC, germaniumGe, a silicon germanium crystal SiGe, gallium nitride GaN or galliumarsenide GaAs, by way of example. For example, the semiconductorsubstrate 500 a may be a silicon wafer. A plurality of identicalsemiconductor dies may be obtained from the semiconductor substrate 500a.

The semiconductor layer 100 a has a planar first surface 101 and aplanar second surface 102 parallel to the first surface 101. The normalto the first and second surfaces 101, 102 defines a vertical directionand directions orthogonal to the vertical direction are lateraldirections.

At least a first and a second trench pattern 410, 420 are introducedinto the semiconductor substrate 500 a from the first surface 101.Further trench patterns may be formed in other portions of thesemiconductor substrate 500 a, e.g. contemporaneously with the first andsecond trench patterns 410. 420. An array isolation region 490, whichconsists of or at least includes a portion of the semiconductorsubstrate 500 a, spatially separates the first and second trenchpatterns 410, 420 from each other. Further array isolation regions 490may spatially separate the first and/or second trench patterns 410, 420from one or more further trench patterns and/or some or all of thefurther trench patterns from each other. Each of the trench patterns410, 420 and further trench patterns may be completely surrounded by anarray isolation region 490 in the lateral directions, wherein each arrayisolation region 490 surrounds one single of the trench patterns.

The first and second trench patterns 410, 420 include array trenches411. At least the first trench pattern 410 includes at least one contacttrench 413, which is structurally connected with the array trenches 411of the first trench pattern 410.

For example, a mask layer may be deposited on the first surface 101 andpatterned by photolithographic means to generate an etch mask with maskopenings exposing portions of the first surface 101 corresponding to thetrenches of the first and second trench patterns 410, 420. Apredominantly anisotropic etch removes semiconductor material of thesemiconductor layer 100 a in the vertical projection of the maskopenings in the etch mask.

FIG. 1A shows the first and second trench patterns 410, 420 and thearray isolation region 490 separating the first and second trenchpatterns 410, 420 from each other. The array trenches 411 may beparallel stripes, wherein semiconductor fins 418 are formed betweenneighboring array trenches 411. The array trenches 411 may have equalwidths and may be equally spaced at a center-to-center distance (pitch)between 20 nm and 500 nm, for example between 150 nm and 250 nm. Forexample, the width d1 may be at least twice the width d3. Each of thetrench patterns 410, 420 may define one or more semiconductor fins 418,for example one thousand or more semiconductor fins 418.

The array trenches 411 of the first trench pattern 410 are assigned to afirst switching device and are formed within a first cell area 441. Thearray trenches 411 of the second trench pattern 420 are assigned to asecond switching device and are formed within a second cell area 442.Array trenches of further trench patterns may be assigned to furtherswitching devices. One, two or more auxiliary trenches 414 extending ina lateral direction intersecting the array trenches 411 may connect thearray trenches 411 of the same trench pattern 410, 420 with each other.

The contact trench 413 is formed in a contact area 449 outside the firstcell area 441. The contact trench 413 may run perpendicular or parallelto the array trenches 411 and may or may not directly adjoin the cellarea 441. According to the illustrated embodiment, the contact trench413 is spaced from the first cell area 441 and one, two or more spacertrenches 412 structurally connect the contact trench 413 with the arraytrenches 411 and/or with one or more of the auxiliary trenches 414. Awidth d2 of the contact trench 413 is greater than the width d1 of thewidest array trench 411. The second trench pattern 420 and/or furthertrench patterns may or may not include a further contact trench,respectively.

The first and second trench patterns 410, 420 are arranged along a firstlateral direction which may be orthogonal to the direction along whichthe array trenches 411 extend. The second trench pattern 420 may bearranged in the projection of the first trench pattern 410 along thefirst lateral direction. For example the cell areas 441, 442 may bearranged along the same lateral axis. Further trench patterns, which arestructurally disconnected from the first and second trench patterns 410,420, may be formed along the same lateral axis.

Referring to FIG. 1B, a gate dielectric layer 205 a may be formed on theexposed semiconductor material of the semiconductor layer 100 a. Theformation of the gate dielectric layer 205 a may include a thermaloxidation of the semiconductor material of the semiconductor layer 100 aor the deposition of a dielectric material, for example silicon oxide,or both. According to an embodiment, providing the gate dielectric layer205 a includes a thermal oxidation of the semiconductor material of thesemiconductor layer 100 a, deposition of a silicon oxide using, e.g.TEOS (tetra ethyl ortho silane) as precursor material, and a furtherthermal treatment. Forming the gate dielectric layer 205 a may includethe formation of a silicon nitride or silicon oxynitride layer and/orthe deposition of other dielectric materials.

A conductive gate material is deposited, which fills the trenches of thefirst and second trench patterns 410, 420. The conductive gate materialmay be heavily doped polycrystalline silicon. According to otherembodiments, more than one gate material is deposited to form a layeredstructure that may include one or more metal-containing layer(s). Thegate material(s) is/are recessed to form, in each trench pattern 410,420 a contiguous gate electrode structure 150. The gate electrodestructure 150 of the two cell areas 441, 442 are separated by a recessand/or polishing process taking place at the first surface 101.

The cross-sectional view of FIG. 1B shows the recessed gate materialforming a contiguous gate electrode structure 150 in a lower section ofthe first trench pattern 410. An exposed surface of the gate electrodestructure 150 has a distance d4 to the first surface 101 in the arraytrenches 411. The distance d4 may be greater than zero, for example in arange from 500 nm to 1.5 μm. Since the recess process may be faster forwider trenches, a distance d5 between the first surface 101 and anexposed surface of the gate electrode structure 150 in the contacttrench 413 may be greater than the distance d4.

A fill material is deposited in a predominantly conformal manner,wherein a thickness of a resulting fill layer 209 a is less than half ofthe width d2 of the contact trench 413 and greater than or equal to thehalf of the width d1 of the widest array trench 411. The fill layer 209a may be a homogenous layer or may include two or more sub layers ofdifferent materials. According to an embodiment, the fill layer 209 a isa homogenous dielectric layer, e.g., from a silicon oxide.

As shown in FIG. 1C the fill layer 209 a completely fills sections ofthe array and auxiliary trenches 411, 414 between the first surface 101and the buried gate electrode structure 150, but only lines acorresponding section of the contact trench 413, thereby leaving a voidin the contact trench 413 above the buried gate electrode structure 150.

An anisotropic etch removes horizontal portions of the fill layer 209 aon the first surface 101 and on the buried gate electrode structure 150in the contact trench 413. In the contact trench 413, the anisotropicetch forms a spacer structure 209 c of the fill material and exposes acentral portion of the gate electrode structure 150. A furtherconductive material, which may be the same material as the gate materialor a different material, is deposited and fills the void in the contacttrench 413. The further conductive material may consist of or containheavily doped polycrystalline silicon and/or one or moremetal-containing layers.

Excess material of the further conductive material outside the void inthe contact trench 413 may be removed, for example by an etch process ora CMP (chemical-mechanical polishing) that may also remove portions ofthe gate dielectric layer 205 a outside the trenches.

FIG. 1D shows resulting dielectric fill structures 209 from the fillmaterial in the array and auxiliary trenches 411, 414 between the firstsurface 101 and the gate electrode structure 150. In the contact trench413 the fill material forms the spacer structure 209 c between the firstsurface 101 and the gate electrode structure 150. A connection plug 195of the further conductive material extends between a plane spanned bythe first surface 101 and the gate electrode structure 150.

For separating the gate electrode structures 150 assigned to differentcell areas 441, 442, conventional approaches use an etch mask exposingthe gate material in an array separation trench and a separation etchremoves material along vertical sidewalls of the semiconductor layer 100a, with the risk that remnants of the gate material at the sidewalls ofthe array separation trench structurally connect and short-circuit theconcerned gate electrode structures 150. In contrast, the abovedescribed recess inherently separates the gate electrode structures 150assigned to different trench patterns 410, 420 above the array isolationregion 490 and outside of trenches. Hence, the method illustrated withFIGS. 1A to 1E provides more reliably separated gate electrodestructures 150, with less effort. In addition, the connection plug 195can be formed self-aligned to the gate electrode structure 150 in thecontact area 449, such that a lithography process for etching contacttrenches to the buried gate electrode structure 150 can be saved.

An embodiment may provide removal of portions of the semiconductor fins418, such that along a second lateral direction orthogonal to the firstlateral direction separation trenches spatially separate sections of thesemiconductor fins 418 adjoining the first surface 101. For example, alithography process provides a cell separation etch mask with openingscrossing the semiconductor fins 418 along the first lateral directionand an anisotropic etch process removes material in the verticalprojection of the openings in the cell separation etch mask.

The anisotropic etch may be or may not be material-selective. Forexample, the etch process may have a high etch selectivity between thematerial of the semiconductor fins 418 and the fill material of the fillstructures 209. The separation trenches may be filled with a dielectricmaterial, which may be the same material as or another than the fillmaterial of the fill structures 209 to form separation structures 175.Another embodiment does not provide separation trenches to define sourceand drain zones within each semiconductor fin 418, but may provide anon-state current flow between neighboring semiconductor fins 418.

A connection wiring 315 may be provided that may directly adjoin boththe connection plug 195 assigned to the first trench pattern 410 andactive transistor areas in remnant sections of the semiconductor fins418 assigned to the second trench pattern 420. According to otherembodiments, the connection wiring 315 electrically connects theconnection plug 195 with source, drain or gate regions of other FETstructures, which are not assigned to the first or second trenchpatterns 410, 420, with terminal pads, with inputs or outputs of otherelectric circuits integrated in the same semiconductor die, with anodeor cathode regions of semiconductors diodes, with collector, emitter orbase regions of bipolar junction transistor.

FIG. 1E shows both the separation structures 175 segmenting uppersections of the semiconductor fins 418 along the second lateraldirection and the connection wiring 315 directly adjoining andelectrically connecting the connection plug 195, which is assigned tothe first trench pattern 410, and active transistor areas in thesemiconductor fins 418 assigned to the second trench pattern 420.

The embodiments include combinations of two or more transistor devicesof the same type or of different types including p channel FETs of theenhancement and depletion type and n channel FETs of the enhancement anddepletion type.

FIGS. 2A to 2C refer to an embodiment of a semiconductor device 500 bwhich may be obtained, by way of example, by the method illustrated inFIGS. 1A to 1E.

According to FIG. 2A, the semiconductor device 500 b may include atleast two semiconductor switching devices, e.g., an enhancement typeIGFET TB and a depletion type IGFET TA, which are arranged in a cascodeconnection. The load paths between the sources s and drains d of theIGFETs TA, TB are arranged in series between drain and source terminalsD, S of the power semiconductor device 500 b, providing an IGFETfunctionality. The gate terminal G of the semiconductor device 500 b orthe output of an integrated gate driver is electrically connected orcoupled to the gate electrode g of the enhancement type IGFET TB. Thesource s of the enhancement type IGFET TB may be electrically connectedor coupled to the gate electrode g of the depletion type IGFET TA. Thedrain d of the enhancement type IGFET TB is electrically connected withthe source s of the enhancement type IGFET TA.

In a blocking mode, each of the IGFETs TA, TB sustains a portion of thetotal blocking voltage. In the conductive mode, the two IGFETs TA, TB,which are electrically arranged in series, may provide an on-stateresistance that is lower or at least in the range of the on-stateresistance of a single IGFET device having a comparable blocking voltagecapability. Since the total blocking voltage can be modified by thenumbers of transistors electrically arranged in series and integrated inthe same semiconductor die in a lateral direction, device parameterslike blocking voltage capability and on-state resistance for IGFETdesigns can be modified without modifying the thickness of semiconductorsubstrates through expensive grinding and polishing processes.

FIG. 2B shows a portion of the semiconductor device 500 b with a firstcell array 451 including transistor cells TC assigned to a firstswitching device that may be, by way of example, the depletion typeIGFET TA of FIG. 2A, and with a second cell array 452 includingtransistor cells TC assigned to a second switching device, which may be,by way of example, the enhancement type IGFET TB of FIG. 2A.

The cell arrays 451, 452 include notched semiconductor fins 180 withsource regions s1, s2 and drain regions d1, d2 oriented to the samesurface side of the semiconductor device 500 b.

The first and second cell arrays 451, 452 are arranged along a firstlateral axis. Within each cell array 451, 452 the transistor cells TCare arranged in a matrix, wherein source regions s1, s2 of a subset ofadjacent transistor cells TC are arranged along the first lateraldirection and the drain regions d1, d2 are arranged along a secondlateral direction orthogonal to the first lateral direction with respectto the source region s1, s2 of the respective transistor cell TC. Thesource regions s1 of the first cell array 451 may be in the projectionof the drain regions d2 of the second cell array 452 along the firstlateral direction, and the source region s2 of the second cell array 452may be in the projection of the drain regions d1 of the first cell array451 along the first lateral direction. In each cell array 451, 452 therespective gate electrode structure 150 includes array stripes 151forming active gate electrodes, wherein the array stripes 151 runbetween neighboring notched semiconductor fins 180 along the secondlateral direction.

Separation structures 175 in the notched semiconductor fins 180 separatesource and drain regions s1, d1 or s2, d2 assigned to the samesemiconductor fin 180 between the same pair of array stripes 151.

First wiring connections WC1 extend along the first lateral directionand may electrically connect the second source regions s2 arranged alongthe first lateral direction in the second cell array 452 with each otherand with a source connector SC. Second wiring connections WC2electrically connect the second drain regions d2 in the second cellarray 452 arranged along the first lateral direction with each other andwith first source regions s1 in the first cell array 451. Third wiringconnections WC3 electrically connect first source regions s1 arrangedalong the first lateral direction with each other and, e.g. with a drainconnector or source regions of a further cell array assigned to afurther switching device integrated in the same semiconductor die. Thesource connector SC may be electrically connected or coupled to a sourceterminal S of the semiconductor device 500 b and the drain connector maybe electrically connected or coupled to a drain terminal D of thesemiconductor device 500 b.

The gate electrode structure 150 in the first cell array 451 furtherincludes a contact stripe 153 connected with the array stripes 151,wherein one, two or more spacer stripes 152 may structurally connect thearray stripes 151 with the contact stripe 153. A connection plug 195 isformed between the first surface 101 and the contact stripe 153. Aconnection wiring 315 directly adjoins semiconductor areas of thetransistor cells TC in the second cell array 452, for example the firstsource regions s1, and the connection plug 195. The connection wiring315 may be structurally and electrically connected with one or more ofthe first wiring connections WC1.

According to FIG. 2C, fill structures 209 above the array stripes 151,auxiliary stripes 154 and the spacer stripes 152 of FIG. 2B spatiallyseparate the gate electrode 150 from the first surface 101 of thesemiconductor portion 100. Outside the first cell array 451, theconnection plug 195 extends between the first surface 101 and the gateelectrode 150 and laterally framed by a spacer structure 209 c of thefill material.

The drain regions d1, d2 are drain impurity zones 120 directly adjoiningthe first surface 101 in first portions of the notched semiconductorfins 180. Source regions 110 are formed in second sections of thenotched semiconductor fins 180 and extend from the first surface 101 upto a distance to the first surface 101 that corresponds to the distancebetween the gate electrodes 150 and the first surface 101. Each sourceregion 110 may be an impurity zone or may include a heavily dopedpolycrystalline first section directly adjoining the first surface 101and a single crystalline second section directly adjoining the firstsection.

The semiconductor portion 100 may further include a substrate layer 140directly adjoining a second surface 102 parallel to the first surface101. The substrate layer 140 may have an impurity type opposite to theimpurity type of the source and drain regions 110, 120. Between thesource and drain regions 110, 120 on the one side and the substratelayer 140 on the other side, the semiconductor portion 100 includes achannel/body layer 115 directly adjoining the source and drain regions110, 120. For transistors of the enhancement type, the channel/bodylayer 115 includes portions of the opposite conductivity type of thesource and drain regions 110, 120 structurally connecting the source anddrain regions 110, 120. For depletion type transistors, the channel/bodylayer 115 includes portions of the same conductivity type as the sourceand drain regions 110, 120 structurally connecting the source and drainregions 110, 120. The channel/body layer 115 may include furtherimpurity zones, e.g., for separating neighboring transistor cells TC orcell arrays through pn junctions.

For depletion type transistors, a suitable voltage applied at the gateelectrode structure 150 fully depletes the portion of the channel/bodylayer between the source and drain regions 110, 120 such that thetransistor cells TC are in an off-state. Otherwise, a current flowsbetween the source and drain regions of each transistor cell TC. Forenhancement type transistors, a conductive channel of minority chargecarriers may be formed in the channel/body layer 115 when a potentialapplied at the gate electrode structure 150 is sufficiently high.

The first, second and third wiring connections WC1, WC2, WC3 maydirectly adjoin the first surface 101 or a plane spanned by the firstsurface 101. Other embodiments may provide a dielectric layer 220,wherein contacts 305 extending through openings in the dielectric layer220 electrically connect the first, second and third wiring connectionsWC1, WC2, WC3 with the source regions 110 and drain regions 120 as wellas the connection wiring 315 with the connection plug 195.

FIGS. 3A to 3C refer to a method providing the gate electrode structure150 using a recess etch mask. As regards introducing a first and asecond trench pattern 410, 420 into a semiconductor layer 100 a, theformation of a gate dielectric layer 205 a formed on the exposedsemiconductor material of the semiconductor layer 100 a and depositionof a conductive gate material 150 a that fills the trenches of the firstand second trench patterns 410, 420 reference is made to the descriptionof FIGS. 1A to 1B, wherein the contact trench 431 is not necessarilywider than the widest array trench 411 but may have, e.g., the samewidth.

After deposition of the gate material, a recess mask layer is depositedand patterned by photolithographic means to form an etch mask 490. Theetch mask 490 may be provided on the deposited gate material 150 a. Thegate material 150 a may be or may not be partially recessed beforeapplying the recess mask layer. For example, the gate material 150 a maybe etched and/or chemically-mechanically polished such that horizontalportions above the first surface 101 are completely removed beforeproviding the recess etch mask 490, which then may be formed directly onthe first surface 101 or the gate dielectric layer 205 a.

The recess etch mask 490 covers at least a portion of the gate material150 a in the contact trench 413 and exposes the gate material in thearray trenches 411 and the auxiliary trenches 414. An isotropic etch maybe performed that recesses the gate electrode material 150 a at least inthe array trenches 411 and the auxiliary trenches 414. At least in aportion of the contact trench 413, the gate material is not recessed. Afill material is deposited that fills the array trenches 411 above therecessed gate material forming the buried gate electrode structures 150.Excess portions of the fill material above the first surface 101 areremoved as described with reference to FIG. 1D.

FIG. 3B shows the fill structures 209 extending between the firstsurface 101 and the gate electrode 150 in the array and auxiliarytrenches 411, 414. At least in a portion of the contact trench 413, anexposed surface of the gate material is flush with the first surface 101and can be electrically connected to a connection wiring in the samewiring plane as the contact, source and drain regions formed between thearray trenches 411.

FIG. 3C is a cross-sectional plane parallel to the cross section lineB-C of FIG. 3B along a spacer trench 412. In the region of the contacttrench 413, a portion of the gate material forms the connection plug195.

FIG. 4 shows a semiconductor device 500 c resulting from the methoddescribed in FIG. 3A to 3C. As opposed to the semiconductor device 500 bof FIG. 2C, the contact trench 413 in FIG. 4 does not provide a spacerstructure of the fill material 290. Instead, the gate material may filla complete cross-section of at least a longitudinal portion of thecontact trench 413. A portion of the gate material forms the connectionplug 195.

FIG. 5A shows a semiconductor device 500 d based on a plurality ofswitching devices electrically arranged in a cascode configuration.According to the illustrated embodiment, the semiconductor device 500 dincludes an enhancement type IGFET E and a plurality of depletion typeIGFETs D1, D2, Dn.

FIG. 5B shows a planar view of the wiring connections of thesemiconductor device 500 d of FIG. 5A following the pattern describedabove. Each of the IGFETs E, D1, D2, Dn may be completely surrounded inthe lateral directions by an array isolation region 490. Each of theswitching devices may include a gate connection as described above. Thegate wiring GC electrically connected to the gate electrode structure150 of the enhancement type IGFET may be electrically connected orcoupled to an output terminal of an internal gate driver circuit or agate terminal.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A semiconductor device, comprising: a first gateelectrode structure buried in a semiconductor portion and comprisingarray stripes inside a first cell array of transistor cells and acontact stripe outside the first cell array, the contact stripestructurally connected with the array stripes; a second gate electrodestructure buried in the semiconductor portion and comprising arraystripes inside a second cell array of transistor cells, wherein an arrayisolation region of the semiconductor portion separates the first andsecond gate electrode structures; and a connection plug extendingbetween a first surface of the semiconductor portion and the contactstripe of the first gate electrode structure.
 2. The semiconductordevice of claim 1, wherein the contact stripe is wider than the arraystripes.
 3. The semiconductor device of claim 1, wherein a fillstructure extends between the first surface and the array stripes and aspacer structure from a material of the fill structure extends along theconnection plug between the first surface and the first gate electrodestructure.
 4. The semiconductor device of claim 1, comprising at leastone spacer stripe structurally connecting the array stripes with thecontact stripe.
 5. The semiconductor device of claim 1, comprisingsemiconductor fins between the array stripes, wherein separationstructures spatially separate sections of the semiconductor finsadjoining the first surface.
 6. The semiconductor device of claim 1,comprising a connection wiring directly adjoining both the connectionplug assigned to the first cell array and sections of semiconductor finsassigned to the second cell array.
 7. The semiconductor device of claim1, wherein the array isolation region completely surrounds the firstcell array in lateral directions parallel to the first surface.
 8. Apower semiconductor device with active drift zone, the powersemiconductor device comprising: a first gate electrode structure buriedin a semiconductor portion and comprising array stripes inside a firstcell array of transistor cells and a contact stripe outside the firstcell array, the contact stripe structurally connected with the arraystripes; a second gate electrode structure buried in the semiconductorportion and comprising array stripes inside a second cell array oftransistor cells, wherein an array isolation region of the semiconductorportion separates the first and second gate electrode structures; aconnection plug extending between a first surface of the semiconductorportion and the contact stripe of the first gate electrode structure;and a connection wiring directly adjoining active semiconductor areas ofthe transistor cells of the second cell array and the connection plug.